Pre-renal azotemia mimicking chronic renal failure in a hypotensive patient

A 56-year-old Samoan man with a documented history of hypertension, who presented with atrial fibrillation and hypotension, quickly developed renal failure with a serum urea nitrogen of 1.370 g/L and a serum creatinine of 92 mg/L. After hydration of the patient, the creatinine value became normal in two days, the urea nitrogen in four days. The urinary creatinine output during the first 24 h of hospitalization was 3.7 g. This case illustrates the rapidity with which unusually large amounts of creatinine (more commonly seen in chronic renal failure) can accumulate and be excreted in pre-renal failure. It also reaffirms the usefulness of the urea nitrogen/creatnine ratio in evaluating the causes of azotemia.